Hitherto, as a working method for thinning a semiconductor wafer, there have been known mechanical and chemical methods such as grinding, polishing (CMP), and etching methods. In all of these methods, adopted is generally a process of sticking a protecting tape onto a semiconductor wafer front face on which a wiring pattern is formed to perform the protection of the wiring pattern and the fixation of the semiconductor wafer, and then thinning the rear face of the semiconductor wafer.
However, the strength and rigidity of the semiconductor wafer become lower as the semiconductor wafer is made thinner. As a result, the semiconductor wafer is broken due to a reduced strength of the semiconductor wafer, or is warped due to a reduced rigidity thereof. Under such a situation, it is necessary to handle semiconductor wafers with sufficient attention. However, even if semiconductor wafers are handled with sufficient attention, there is caused a problem that the semiconductor wafers are frequently broken so that the yield thereof falls. Additionally, there is caused a problem that the semiconductor wafers cannot be carried with a wafer carrier or the like by due to the reduced strength and rigidity of the semiconductor wafers by the thinning-work thereof, so that work efficiency drops.
Against these problems, there is suggested a method of fixing a reinforcing-plate through a double-side adhesive sheet onto a semiconductor wafer front face on which a pattern is formed and then subjecting the rear face of the reinforced semiconductor wafer to thinning-work (JP-A-2002-75937). Since the reinforcing-plate is easily separated after the semiconductor wafer is subjected to the thinning-work according to this method, this publication suggests using a peelable adhesive type double-side adhesive sheet which can be peeled by an external energy such as heat or ultraviolet ray. For example, in the case of the peeling-effect based on heat about the above-mentioned peelable adhesive type double-side adhesive sheet, the separation of the reinforcing-plate is started by the bubbling of the adhesive layer by action of the heat. In the case of the peeling-effect based on ultraviolet rays, the separation of the reinforcing-plate is started by the curing of the adhesive layer irradiated with the ultraviolet rays. The above-mentioned external energy is given to the whole of a face of the peelable adhesive type double-side adhesive sheet when the reinforcing-plate is separated.